The primary objective of this proposal is a biochemical and morphological study of the development of the blood-ocular barriers to proteins in the embryonic and post-embryonic chicken. We will investigate the mechanisms responsible for preventing the appearance of two enbryonic plasma proteins in the vitreous humor at a time in embryonic development when transport of other labelled plasma proteins into the vitreous humor can be directly demonstrated. These specifically "excluded" proteins will be purified from embryonic plasma and labelled with 125I or used as antigens for the production of specific antibodies. These preparations will be used to localize by autoradiography and immunohistochemistry the barriers which prevent the penetration of these molecules into the eye. In addition, we will use light and electron microscopy to map the routes of penetration of the enzyme tracers, microperoxidase (1,880MW), horseradish peroxidase (40,000MW), and catalase (240,000MW) from the vascular system into the vitreous and aqueous humor of embryonic and hatched chickens. Once these routes of penetration have been defined, we will follow the development of the blood-ocular barriers by examining, with freeze-fracture and thin section of electron microscopy, the morphological changes which correlate in time and location with reduction of protein penetration into the ocular fluids. As part of these studies we will also describe the functional development of the aqueous outflow system by intraocular injection of fluorescein into embryos of different ages. These experiments will provide a systematic study of the development of the blood-ocular barriers to proteins and should contribute to our understanding of the mechanism responsible for the breakdown or absence of one or more of these barriers in many ocular diseases.